Screening Lettuce Cultivars for Growth, Yield, And Tipburn in Hydroponic System Under Greenhouse Conditions

Yubraj K C

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ag Science and Natural Resources

Date of Award

1-10-2024

Abstract

Cultivars with stable horticultural traits are imperative for successful hydroponic production of lettuce under greenhouse conditions generally characterized by a constant fluctuation in the environmental factors including light, temperature, and humidity. The objective of this study was to evaluate a set of lettuce cultivars for growth, yield, and tipburn incidence in a hydroponic system under greenhouse conditions over different seasons. During each growing cycle in winter, spring, summer, and fall, seeds of 40 cultivars of lettuce of different types were germinated in rockwool cubes inside plug trays and were subsequently grown for approximately three weeks. Mature seedlings were transplanted onto nutrient film technique (NFT) hydroponic systems and were grown with an optimum nutrient solution. The experiments were carried out as a randomized complete block design with three replications. At commercial maturity stage (30–40 days after transplanting), lettuce plants were evaluated for tipburn incidence and representative lettuce heads were sampled for measurements of fresh weight, leaf number per plant, leaf area, and dry weight. Highly significant effects of cultivar, season, and their interaction were observed on the fresh yield and its components as well as tipburn incidence. Averaged fresh yield ranged from 1.74 kg/m2 to 10.44 kg/m2 across the four growth cycles. Average yields achieved in the spring season were significantly higher than those in the winter season. Cultivars Tropicana and Salvius had the highest yield in winter, spring, and fall while the top yielding cultivars in summer were Green Star and Bergam’s Green. Across all four growth cycles, up to 20 cultivars exhibited yields lower than the grand means (4.12 kg/m2). Tipburn incidence was more pronounced during the summer growth cycle where 37 out of the 40 cultivars evaluated showed some level of tipburn. Cultivars Flashy Trout Back, Little Gem, and Dragoon exhibited the most severe tipburn incidence independently of the growth cycle. In contrast, cultivars Oscarde, Rouxai, and Bergam’s Green showed no tipburn incidence across all four growth seasons. Thus, selectively growing a lettuce cultivar performing well in a respective season in terms of both yield and tipburn incidence can prove to be an effective and efficient production practice.

Advisor

Desire Djidonou

Subject Categories

Agriculture | Life Sciences

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